1. Field
This invention relates to audio systems, more particularly to determining speaker characteristics and matching of audio system components.
2. Background
High-end audio systems typically include various signal production components, such as tuners, CD players, tape decks, and turntables, amplifying components such as receivers and amplifiers, and sound generation elements, usually various configurations of speakers. Connoisseurs of audio systems often buy the components from various manufacturers, or change components of the same manufacturer over the system lifetime.
High-quality equipment available today has commensurately high-quality component signal levels, with broad audio bandwidth and ultra-low distortion. Interfaces exist between the signal generation equipment and the amplification equipment. However, the interface between the amplification equipment and the sound generation equipment is not as well characterized. Current state-of-the-art speakers have nominal impedances of 4 or 8 ohms, matching the output impedance of the amplifier. Beyond that, no general standardization exists.
Speaker characteristics can be derived in several ways. The characteristics can include such performance aspects as maximum power handling capacity, impedance profile, and equalization requirements. Users typically adjust for these characteristics manually, which can be subjective and imprecise, as well as time-consuming. These adjustments typically do not account for the maximum power capacity, except for the manual volume control. Overpowering the speaker can damage or ruin it, resulting in a ‘blown’ speaker.
Methods have been suggested to compensate for this lack of speaker characterization in audio systems. For example, U.S. Pat. No. 4,592,088, issued May 27, 1986 discloses a method of placing a microphone within a speaker enclosure or housing. The output of the microphone is fed back to the amplifier, providing control of the amplifier output in view of the speaker output. However, this approach relies upon the quality of the microphone as well as the extra interface between microphone and amplifier.
In another example, found in U.S. Pat. No. 5,818,948, issued Oct. 6, 1998, the speaker is powered and communicates along a USB interface. The USB controller receives the audio data along this bus. It also detects when there is no data and manages power to the speakers based upon their status of receiving or not receiving any signals. However, there are no control communications with regard to the speaker characteristics.
Another example can be found in U.S. Pat. No. 5,532,556, issued Jul. 2, 1996. This disclosure includes multiplexing audio and control signals together between audio function units. The control signals do not include information about speaker characteristics, beyond their presence and their status as receiving or not receiving audio signal.
Therefore, a need exists for a method and apparatus for providing speaker characteristics along already-established interfaces in audio systems.